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July 20, 2011

Fourth Moon Discovered Around Pluto

by Sam Savage

NASA said on Wednesday that astronomers have discovered a fourth moon orbiting the dwarf planet Pluto.

The new moon was uncovered while using the Hubble Space Telescope.

"I find it remarkable that Hubble's cameras enabled us to see such a tiny object so clearly from a distance of more than 3 billion miles," Mark Showalter of the SETI Institute in Mountain View, Calif., who led this observing program with Hubble, said in a press release.

NASA said the new moon has an estimated diameter of 8 to 21 miles. Pluto's moons have varieties of ranges in diameter.

The dwarf planet's largest moon is 648 miles in diameter, while its smaller moons are between 20 and 70 miles in diameter.

"This is a fantastic discovery," New Horizons' principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado said in a press release.

"Now that we know there's another moon in the Pluto system, we can plan close-up observations of it during our flyby."

According to NASA, Pluto's entire moon system is believed to have formed by a collision between Pluto and another planet-sized body early in the history of the solar system.

"This surprising observation is a powerful reminder of Hubble's ability as a general purpose astronomical observatory to make astounding, unintended discoveries," said Jon Morse, astrophysics division director at NASA Headquarters in Washington.

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Image Caption: Two labeled images of the Pluto system taken by the Hubble Space Telescope's Wide Field Camera 3 ultraviolet visible instrument with newly discovered fourth moon P4 circled. The image on the left was taken on June 28, 2011. The image of the right was taken on July 3, 2011. Credit: NASA, ESA, and M. Showalter (SETI institute)